The present invention relates to a guide-bar device for multi-spindle lathe with a barrel operable to be indexed by said multi-spindle lathe and comprising a plurality of guiding tubes for enclosing a bar stock to be machined set into rotation within a fluid by said multi-spindle lathe, a rear part of said bar stock being supported by a feeding piston for advancing said bar stock toward a spindle of said multi-spindle lathe.
Such a guide-bar device for multi-spindle lathe with a distributor of fluid for advancing the feeding piston toward a spindle of the multi-spindle lathe is known from the published european patent application No. EP 0 108 182. At the time when a new bar stock to be machined is to be introduced in its guiding tube, the feeding piston is retracted and received entirely within a housing of the distributor. The distributor with the feeding piston is then rotated in order to present an opening in front of the empty guiding tube in which the new bar stock to be machined is to be introduced and the new bar stock is loaded in its guiding tube through this opening. However, the operation of retracting the feeding piston for permitting a new bar stock to be loaded in its guiding tube necessitates a stop of the multi-spindle lathe which increases the machining time and the new bar stock has to be introduced axially from the rear part of the distributor which is place consuming.
From the published european patent application No. EP 0 121 638 there is also known a guide-bar device for multi-spindle lathe similar to the preceding one. At the time of loading a new bar stock to be machined, the feeding piston of the empty guiding tube to be loaded is retracted within an extension tube located axially in front of the rear opening of the guiding tube and this extension tube with the feeding piston is then retracted laterally for liberating the rear opening of the empty guiding tube thus peritting the new bar stock to be presented laterally in front of this rear opening and axially engaged in the guiding tube. However, like in the preceding case, the operation of retracting the feeding piston for permitting a new bar stock to be loaded necessitates a stop of the muti-spindle lathe.
In the modern multi-spindle lathe, one seeks to reduce to a minimum the unproductive times like the stop of the lathe for permitting the feeding piston of a guiding tube in which a new bar stock to be machined is to be loaded, to be retracted, in order to accelerate the cycle of machining and to increase the rate of production. Moreover, the multi-spindle lathes are such that the different bar stocks are not exhausted simultaneously. Taking into account the tolerances in the length of the pieces which are machined from the bar stocks and that the different bars have different lengthes, it is to be seen that, in the time, the bar stocks are exhausted at random.